This invention relates to fluid pressure-intensifying devices and more particularly, relates to a fluid intensifier having a double-acting piston that operates with minimal shock at the point of transition in direction of motion of the double-acting piston.
In systems requiring high-pressure fluids, for example, water jet cutting or drilling, it is common to use an intensifier that receives fluid, e.g., water, from a low-pressure source and increases the pressure of the fluid to the desired pressure. A typical intensifier will include a low-pressure or working cylinder with a double-acting piston therein, the low-pressure cylinder having opposing high-pressure barrels affixed to it. A high-pressure piston is slidably mounted within each of the high-pressure barrels and the high-pressure pistons are attached to the low-pressure piston such that the high-pressure pistons reciprocate in unison with the reciprocation of the low-pressure piston. A working fluid, such as oil, is alternately pumped into opposite chambers of the low-pressure cylinder to provide a reciprocal motion of the low-pressure piston and low-pressure water is alternately fed into the opposing high-pressure barrels to be compressed and forced from the cylinder by the high-pressure piston acting in conjunction with the low-pressure piston. Typically, the high-pressure piston has a cross-sectional area much smaller than that of the low-pressure piston. It is therefore possible to obtain an increase in the pressure of the water within the high-pressure cylinder while using a lower pressure hydraulic system to move the working piston.
In a reciprocating pressure intensifier there is a tendency for shock at the end of the high-pressure piston at the moment of reversal of direction of the high-pressure piston motion. It is desirable to provide a system of controlled reversal of the direction of motion of the high-pressure piston that minimizes this shock. One such system is shown in the U.S. Pat. No. 4,029,440 issued to Olson, June 14, 1977. The Olson system utilizes a method of controlling the pressure on either side of the low-pressure piston to provide a smooth transition in direction of the low-pressure piston. The pressure control is accomplished by controlling the area of the valve surfaces of a control valve, which controls the flow of fluid into the low-pressure cylinder, in accordance with a prescribed formula set forth in the Olson patent. While the Olson system works in theory, it is believed more practical to control the reversal to eliminate shock through control of the flow rate of working fluid instead of the pressure.
It is therefore an object of the present invention to provide a fluid intensifier including a double-acting piston assembly, which minimizes the shock experienced by the high-pressure piston assembly at the time of reversal of direction of motion of the piston assembly.
It is a further object of the invention to provide a fluid intensifier in which the flow rate of working fluid in the low-pressure cylinder is controlled to accomplish the smooth transition of direction of motion of the working piston.